Retort system for oil shales and the like

ABSTRACT

In apparatus for retorting oil shale, oil sands and similar materials wherein finely divided solids residue is used as a heat carrier and is heated in a vertical pneumatic conveyor-burner, mixed with fresh finely divided solid feed, product distillation vapors are removed from the mixture, and the solid distillation residue is returned to the conveyor-burner, the improvement whereby the propellant gas is introduced axially to the bottom of the conveyor-burner and the cool heat carrier is introduced thereinto from a concentric annular chamber thereabout through slits or openings in the propellant gas conduit by means of a flow of a control gas. Other specific improvements of portions of the retorting apparatus and solids circulating system are examplified and claimed, especially a screw conveyor-mixer retorting chamber.

United States Patent Schmalfeld et al.

[151 3,655,518 [4 Apr. 11,1972

[54] RETORT SYSTEM FOR OIL SHALES AND THE LIKE [73] Assignees:Metallgesellschaft Aktiengesellschaft, Frankfurt; RuhrgasAktiengesellschaft, Essen, Germany [22] Filed: Nov. 19,1969 [21]Appl.No.: 877,996

[30] Foreign Application Priority Data Nov. 20, 1968 Germany ..P 18 09874.3

I 56] References Cited UNITED STATES PATENTS 3,251,751 5/1966 Lindahl eta1 ..201/20 X 3,501,394 3/1970 Lyons ..208/l1 3,281,349 10/1966 Evans..208/1 1 3,535,209 10/1970 Ledent ..20l/31 X 3,140,240 7/1964 Fowler..20l/3l X 2,983,653 5/1961 Danulat et a1 ..201/33 X 2,788,314 4/1957Schmalfeld et a1 ..20l/3l X Primary Examiner-Norman Yudkoif AssistantExaminer-David Edwards Attorney-Burgess, Dinklage & Sprung [57] ABSTRACTIn apparatus for retorting oil shale, oil sands and similar materialswherein finely divided solids residue is used as a heat carrier and isheated in a vertical pneumatic conveyor-burner, mixed with fresh finelydivided solid feed, product distillation vapors are removed from themixture, and the solid distillation residue is returned to theconveyor-bumer, the improvement whereby the propellant gas is introducedaxially to the bottom of the conveyor-burner and the cool heat carrieris introduced thereinto from a concentric annular chamber thereaboutthrough slits or openings in the propellant gas conduit by means of aflow of a control gas.

Other specific improvements of portions of the retorting apparatus andsolids circulating system are examplified and claimed, especially ascrew conveyor-mixer retorting chamber.

7 Claims, 4 Drawing Figures Pmmnmmn 1972 3,655 518 sum 1hr 2 lwefa wm.scmwem HANS somaes nammc. AANS PATENTEDAPR 1 1 :972

SHEET 2 OF 2 lnren/ora PAUL SCHHALFHLD HANS SQHHEQS b HEANZAQH AANSSER lD gram Portions of the retorting system of this invention are similar toapparatus disclosed in U.S. Pat. Nos. 2,788,314; 3,056,248 and2,983,653.

PREAMBLE Recently there has been an intensification of efforts todrydistill solid hydrocarbonaceous materials such as bituminous coals,oil shales, oil sands and the like to produced oils, which 'maybefurtherconverted by hydrogenation and conventional refining toproductssimilar to natural petroleum products, e.g. gasoline. 'Suchefforts are being carried on particularly in countries that do not havea cheap and adequate supply of .petroleum, but do have large, easilyworkable deposits of coal,

oil shale, or oil sand. In order for an artificial petroleum of thiskind to be ableto compete with natural petroleum, the content of bitumenor oil in the starting material must be relativelyhigh, and if possibleshould be at least 8 percent, and

preferably more than 10 percent. The starting material should lationofsuch hydrocarbonaceous material, because the residence time of thedistillate vapors in such units is usually too long and accordingly theformation of gas and residual coke is too great. Shaft furnacesoperating with scavenging or stripping gas heating or by internalcombustion are not suitable'either, because they, require that thestarting material be inlumps, and because the distillate vapors producedin them are diluted by the scavenging gas or combustion gas.

Neither can the-known methods for the dry distillation of afinely;granular starting material in one-stage or multi-stage fluidizedbeds be used, because the distillate vapors are diluted by thefluidizing gas. If the fluidizing gas is produced bythe partialcombustion of the starting material or by the admixture of hotfluegases, the distillation gas then contains nitrogen. Thisnecessitates a considerable enlargement of the condensation apparatusand diminishesthe value of the distillation gas by making it unusabledirectly as a pipeline (e.g. public utility) gas, as a source ofhydrogen forhydrogenating, or as a synthesis gas.

It is known to carry out the dry distillation of bituminous andpetroliferous materials by means of circulating heat carriers. Ceramicballs or steel balls are used as the heat carriers, whose heat istransferred to the material to be distilled by direct mixing and contacttherewith, as in a rotating tube. This procedure'has been known for sometime, but it has not been widelyused because the heating and transportof the heat carrier balls through the heater and the rotating tube orkiln is complicated and expensive.

'The use of finely divided heat carrying agents offers importantadvantages, especially if the solid residue from the distillation'of thefinely granular starting material can be used as the heat carrier.Processes and apparatus are known which heat'finely granular heatcarriers in a pneumatic conveyor or in a fluidized bed.

Processes andapparatus are also know in which the heat carrier and theraw hydrocarbonacous material are mixed by feeding them together into ashaft retort, thereby heating the starting material and distilling it.The vapors and gases that are released support the fluidization and themixing together of theheat carriers and the raw material. But thismethod of effecting'mixing in a shaft furnace is not satisfactory whenthe quantities of raw material and heat carrier to be processed aregreat. This retorting method also causes increased formation of coke andgas, thereby resulting in considerable losses in the yield ofrecoverable oils.

The heating of very large quantities of circulating finely granular heatcarriers in a fluidized bed requires a large capital investment andfrequently results in unsafe operation. Heating in a pneumatic conveyoris therefore to be preferred.

THIS INVENTION The invention is directed to an apparatus for the drydistillation of bituminous or petroleum-containing materials such ascoal, lignite, oil shale, oil sand or the like in a finely granularstate and the winning of a distillate therefrom. The material to bedistilled is heated by means of being thoroughly mechanically mixed witha circulating, finely divided heat carrier which is thereafter separatedfrom the distillationvapors along with the solid distillation residue,heated in a pneumatic conveyor, and returned to the distillationapparatus.

The requirements for a high oil yield with a low formation of coke andgas, a rapid and uniform heating of the starting material and a rapidremoval of the distillate vapors from the distillation zone areeffectively met by this invention.

The apparatus according to this invention consists of a verticalpneumatic conveying and heating unit for the particulate heat carrier tothe bottom end of which a free-oxygen containing gaseous propellant isfed axially as through a venturi tube and finely granular thermalcarrier is introduced thereinto from a concentric annular chamberthereabout through slits by means of a flow of a control gas.

A separator at the upper end of the conveyor is divided by a wallextending downward from the top into a separating chamber and asecondary chamber containing the discharge for the propelling gas andproducts of combustion, and a bottom solids collecting chamber that iscommon to both.

A distillation chamber is connected at its input end to the heat carrierdischarged from the separator. It also receives the raw material or feedthat is to be distilled. At its discharge end, one conduit carries awaythe hot mixture of thermal carrier and fresh solid distillation residueand another conduit carries away the distillate vapors. The distillationchamber has a screw conveyor or the like to force and mix the solidsalong the length thereof.

An intermediate reservoir. or hopper is connected at one end to thedistillation chamber and at the other end to the annular chamber at thebottom of the conveyor.

A dust gas separator is used to remove fines from the distillationvapors after which they are condensed in a product recovery system inwhich the vapors are condensed by spraying them with previouslyseparated and cooled condensate.

Another dust separator cleans the products of combustion discharged fromthe conveyor-separator and the gas is then utilized in heat exchange toheat the incoming propellant gas and/or in a waste heat boiler.

The particulate solids removed from the process are cooled, preferablywith water, in a solids cooler.

The finely divided solid distillation residue which serves as the heatcarrier is carried and simultaneously heated in a vertical pneumaticconveying and heating unit and then is separated from the combustiongases by free fall and inertial ejection in a separating chamber, anddelivered to a mechanical mixer in the distillation chamber. In themixer the thermal carrier, heated to 700 C., for example, is combinedwith the from chemically bound water. The formation of light crackedgases while this is taking place is extremely slight.

The mixture of thermal carrier and fresh distillation residue flows fromthe distillation chamber into an intermediate reservoir or hopper forthe after-distillation of the feed material and for the driving ofhydrocarbon vapors from the interstices and pores of the solids as bythe injection of water vapor returned light distillation gases into themixture. The solids are then fed back into the bottom part of thepneumatic conveying and heating unit, thereby completing the cycle ofthe thermal carrier through the heating and distillation steps.

The apparatus of this invention permits an effective and simpledistillation of finely granulated oil-bearing materials, thecondensation of the distillation vapors, and a good recovery of heatfrom the waste gas from the heating of the thermal carrier. Thedistillation vapors from the mixerdistilling chamber are processed in acooling system providing for several stages of contact of the distillatevapors with their own cooled condensate, while the cooling of gases fromthe heater-conveyor is performed in an air preheater and/or a waste-heatboiler.

The specific investment costs of large units embodying this inventionare low. The consumption of heat and power by such units is also low.

THE DRAWINGS FIG. 1 is a flow diagram of an installation according tothe invention;

FIG. 2 is a sectional view in elevation of the distillation chambertaken along the axis thereof and showing in particular the mixer-screwconveyors;

FIG. 3 is a sectional view of the distillation chamber takenperpendicular to the axis thereof; and

FIG. 4 is a horizontal sectional view of the conveyor-solids separatorin one alternative embodiment of this invention.

DESCRIPTION FIG. 1, is the vertical pneumatic conveying and heatingunit, 2 is the conveyor-separator for the separation of the thermalcarrier from the combustion gases, 3 is the mechanicalmixer-distillation chamber and 4 is the intermediate reservoir when thesolids are finally stripped of hydrocarbon gases.

Separator 2 and the retort-mixer 3 are connected by the feed line 5,which in its lower portion has a closing and flow regulating slide valve17, thereby permitting a dense, gasblocking accumulation of solids inline 5 above the valve. In like manner, the intermediate reservoir 4 andthe conveyorburner unit 1 are connected by a feed line 7, which has aclosing and flow regulating slide valve 25 in its lower portion, thusalso creating a dense, gas-blocking accumulation of the solids above thevalve 25. These blocking accumulations in the lines 5 and 7 separate theretort-mixer 3 and the intermediate reservoir 4, in which the distillatevapors and a gas of high heat value flow, from the bottom portion of theconveyor-bumer unit 1 in which there is air, and from the separator 2 inwhich combustion gases are flowing.

The combination conveyor and heating unit 1 is constricted in its bottomportion where the mixture enters through slits or openings 9 into theconveying tube 1 which is constricted into venture at its entrance atthe openings 9. Propellant air, which is preferably preheated isintroduced from the bottom by conduit 10 from which it flows upward,taking with it the mixture flowing in through the openings 9, burningthe carbon contained in or attached to the mixture and thereby heatingthe mixture to the desired temperature of, for example, 700 C. If themixture should not contain enough carbon to heat it sufficiently,additional fuel is introduced into the propellant air through line 65and nozzle 66, in the form, for example, of gas, waste oil or coat dustin a proportioned amount.

The combustion takes place very rapidly and the heat that is released isimmediately transferred to a great extent to the solids of the mixture.Overheating or great temperature differences between the combustiongases and the solids does not occur. This rapid temperature eqalizationalso makes it possible to preheat the propellant gas to a hightemperature, so that excess air can be reduced to a minimum. The rate offlow of air and the rate of flow of any fuel that may be added areadjusted so that no more than the required heating of the mixture isachieved in the conveying unit 1.

Conveying unit 1 is generally 20 to 40 m. long and it is desirable thatit flare from the bottom to the top, either at a constant rate or in astep-wise manner. In the bottom part the velocity of the air orcombustion gases must be higher, e.g., 30 to 40 m./sec., in order toaccelerate the mixture and in the upper part the velocity can drop to 15to 25 m./sec.

The solids from reservoir 4 and feed line 7 run from the annular chamber11 surrounding the conveyor unit 1 to the openings 9 in the latter. Itis desirable for each opening or slit to receive a controlled feed ofsecondary propellant-control air through the nozzle 53 to drive themixture in as well as control, by its rate of fiow, the amount ofmixture which it injects. In this manner the mixture is introducedaround the entire periphery of the conveyor unit and charges it evenly,which is especially important where the diameter of the conveyor isgreat, e.g., 1 meter or more. Since the rate of flow of the propellantair is individually adjustable at each slit, the recirculated materialcan be introduced in relatively greater amounts at the individual slits,if this becomes necessary.

It is very important to separate the conveyed and hot solids from thepropellant gas in such a manner as to prevent abrasion of the apparatuswalls and the formation of any large amount of fine debris. Thisrequirement is met by the arrangement of the conveyor-separator 2. Thevertical conveyor unit empties into a greatly expanded separatingchamber 13 of unit 2, which has from 5 to 20 times, and preferably 7 to12 times the cross-sectional area of the conveyor. The velocity of thepropellant gases drops greatly in this chamber. The flow of gas isobliged to pass around a vertical partition wall 12 which extendsdownward from the cover, so that the solids are ejected from it becauseof the abrupt change in direction. The gas thus separated flows upwardlythrough the adjacent chamber 14 of unit 2 to an outlet 60.

Separator 2 is designed in its lower portion so as to servesimultaneously as a collecting reservoir or hopper 15 for the hotsolids. Hopper l5 communicates with both the large separating chamber 13and with the smaller adjacent chamber 14. Chamber 14 can be made largeror smaller by varying the position of the partition 12. This may beimportant because the upward velocity of the hot combustion gases inchamber 14 is determined by the cross section of this chamber. Thisupward velocity, in turn, is what determines the amount of the finelydivided solids that are separated or fall out into hopper 15.

The distance between the cover of the separating chamber 13 and the topedge of the vertical conveyor 1 amounts, according to the invention, tofrom 3 to 10 m., and preferably 5 to 7 m. At this distance practicallyno wear is observed in the cover of the separator. The separator ispreferably provided with a wear-resistant ceramic lining.

A cyclone separator can be used instead of the separator 2, to thebottom of which a collecting hopper can be connected. In this case theupper end of the conveyor is turned to the horizontal and connected tothe cyclone separator.

A narrow feed line 5 runs from the lower portion or collecting hopper 15to the/input of the mechanical mixer-retort 3. In the lower portion ofline 5 is a slide valve 17 by which control can be exercised over theamount of heated solids that are continuously fed to the mixingmechanism. Valve 17 provides for the formation of dense accumulation ofthe solids above the valve. To accommodate thermal expansion, it isdesirable for feed line which is preferably ceramically lined to have anexpansion joint 16 above valve 17 which joint can also be equipped witha feed line 18 for an auxiliary gas, such as water vapor.

The finely granular feed to be distilled, e.g. tar, sand, oil shale, orasphalt is fed from the hopper 19 through line 20 into the distillationchamber 3, in which it is rapidly and energeti' cally mixed with hotsolids from conduit 5. Within a few seconds the finely granular rawmaterial is raised by rapid heat transfer to a prescribed temperaturebetween 450 and 650 C., so that the bitumen is decomposed and the oilsare released in vapor form by dry distillation. At the same time themoisture and the chemically bonded water in the solid feed are releasedin vapor form. In addition, a small amount of distillation gas develops,amounting to about 5 to 100 standard cubic meters, and usually to to 40standard cubic meters per ton of starting material.

The mixer-retort 3 is illustrated in longitudinal section in FIG. 2 andin cross section in FIG. 3. It has two shafts 21 which rotate in thesame direction, each bearing two vanes 22. The vanes of the two shaftsare 90 out of phase and interplay with one another and carry thematerial being mixed around the two shafts. This circulation is producedby the fact that one vane. of the mixing shaft strips the material beingmixed from the other mixing shaft, carries it around the shaft in itsown area of movement, and yields it back to the other mixing shaft. Inthe stripping action the space filled with the material being mixedconstantly changes its form, the material in the marginal portions beingpushed to the interior and the material in the inner portions beingpushed to the margin.

The vanes 22 are preferably mounted on the shafts in a spiral or wormmanner and thus also advance the mixture forward, axially along theshafts. The spiral shape of the vanes also promotes a more uniformstressing of the mixing shafts and of the transmission that drives them.The forward movement of the mixture can be aided by tilting the mixingshafts downward from the horizontal by 5 to 45, preferably to 30. Theinterplay of the vanes of the two shafts produces a mutual cleaning ofthe shafts on all but a lens-shaped cross section around the two vanesof each shaft. If deposits in this lens-shaped cross section causetrouble, the vanes themselves can be bent or curved accordingly. Thevanes of the two shafts additionally clean the mixer housing in theareas of their movements.

The vanes 22 are best welded directly onto the mixing shafts 21. It isadvantageous to avoid making them continuous so as to prevent damage bythermal expansion. The vanes are therefore interrupted by by gaps of lto 10 mm., preferably 2 to 5 mm., at intervals of 100 to 500 mm.,preferably 150 to 300 mm. Continuous vanes can also be interrupted bynotches extending nearly to the welding seam and can be made moreelastic. The vanes and mixing shafts are exposed to only slight wear,and can be made of ordinary steel or from a material of slightly higherwear resistance. It is important, however, to equip the edges of thevanes with a highly wear resistant deposit as by welding material, or tomake them of hard steel inserts that are replaceable and can be fastenedon by screws, clamping or welding.

Distillation chamber 3 has to handle material with an averagetemperature of 450 to 650 C., and only in exceptional cases does it comein contact with heated solids of a temperature of up to 750 C. To coolshafts 21, it is desirable to use hollow shafts to which a coolant isfed through a pipe extending all the way to the end of the bore in thehollow shaft, returning it through a bore around the infeed pipe. Wateris normally used as the coolant. To keep the heat loss because of thecooling of the mixer shafts to a minimum, circulating oil can be usedhaving a temperature around 200 to 250 C., or some what similar coolantsuitable for high temperatures can be used. It is best to leave theother parts of the mixer uncooled.

The mixer shafts 21 equipped with the spiral vanes 22 advantageouslyhave short spiral sections 54 at the inlet, so as to positively feed thesolids. The spiral sections 54 and the vanes 22 of the mixer shafts 21are connected to one another by transitional pieces of appropriateshape. The raw feed can also be blown in together with returned lightdistillation gases.

These gases can also be used for the purpose of more rapidly removingthe vapors and gases formed in the mixer.

The housing 55 of the mixer 3 is preferably insulated and equipped witha masonry lining in the bottom part and in the side parts, and is givenan external covering of metal plate welded to form a hermetic seal. Thecover is also preferably insulated. The cover plate, however, can alsobe welded on without inside insulation, or it can be at least partiallyattached by screws, so as to be easily removed for inspection of theinterior of the mixing mechanism. The cover plate as illustrated isexternally insulated.

Between the area of movement of the mixer shafts 21 and the cover plate,a free gas collecting chamber 56 is left so as to permit a more readypassage of the vapors and gases formed in the mixer. This chamber 56 isenlarged at the outlet end of the retort 3 to form a dome 50 to draw offthe vapors and gases to the condensation apparatus. This suppresses theentrainment of dust into the condensation apparatus. Chamber 56 isadvantageously constructed in such a manner that the velocity of thevapors and gases does not exceed 10 m./sec., if possible,

while it can increase to 20 m./sec. and more in the pipe 51 leading tothe condensation or product recovery apparatus. The velocity in chamber56 must also not be too low, because a long residence time of the vaporsfavors secondary reaction, particularly of the high-boilinghydrocarbons. Distillation gas fed back into mixture-retort 3 supportsthe rapid removal of the vapors and gases and suppresses secondaryreactions.

The mechanical mixer-retort 3 with the two mixer shafts 21 revolving inthe same direction permits the rapid and intense mixing of the solidseven at high throughput, and permits distillation within a few secondswhen large amounts of finely granular heat carrier. The abrupt heatingachieved prevents the extensive decomposition of the oil vapors andmakes possible an optimum yield of liquid hydrocarbons from the startingmaterial.

Pneumatic mixing systems have proved impractical at high flow ratesbecause large amounts of steam or returned distillation gases arerequired for the pneumatic propulsion. This places an unnecessary burdenon the condensation apparatus. Mechanical mixers of other kinds do notmix rapidly or intensely enough, and they excessively comminute thematerial and are not self-cleaning.

The present invention, however, is not necessarily directed to the useof a mixer having 2 mixer shafts revolving in the same direction, and insome cases simpler mixers using vertical mixer shafts can be used.

The starting material is substantially completely distilled in thedistillation chamber 3 and, still mixed with the heat carrier, it flowsdown through line 23 at the end of the mixer into an intermediate hopper4, where the mixture accumulates, the transfer of heat from the heatcarriers to the starting material is completed, and the distillation ofthe starting material is completed.

The solids are continuously drawn from hopper 4 through conduit 7 to theannular chamber 11 of the vertical conveyorburner 1. In the bottom partof the conduit 7 there is provided a slide valve 25 with which the rateof flow of the mixture into the annular chamber 11 is controlled. Valve25 brings about the formation of a dense accumulation of the solidsabove the valve and up into the intermediate hopper 4.

The intermediate hopper 4 tapers towards conduit 7. In this taperedportion it is desirable to install a diffuser 26, in the form, forexample, of a tubular ring with outlet orifices, so that steam orreturned light distillation gas can be fed through line 27 anddistributed by means of the diffuser 26 into the solids. The steam orgas introduced in this manner drives hydrocarbon vapors out of theinterstices and pores of the solids. According to the invention, thetime of stay of the solids in the intermediate hopper forpost-distillation, the driving out of hydrocarbon vapors and thecompensation of certain irregularities that may occur in the circulationof the solids is about 0.5 to 5 minutes, preferably 1 to 2 minutes. Thesize of the free gas space in hopper 4 is desirably at lease equivalentto a possible detention time of the solids of l to 2 minutes, to permitaccumulation thereof in case of a process interruption. Hence, thehydrocarbon vapors would normally flow only slowly through the free gasspace in the intermediate hopper, and could be decomposed by secondaryreactions. Consequently it is desirable to introduce steam ordistillation gas in such a quantity that the detention time of thehydrocarbon vapors in the free gas space of the intermediate hopper doesnot exceed 1 to 2 seconds.

The hydrocarbonaceous feed material has a particle size of less than 6mm., and preferably less than 4 mm. If the grains decrepitate easily, afeed grain size of up to 2 mm. can be used. The maximum particle size isdetermined by the requirement of performing the distillation all the wayto the center of the grains during the short time of stay inmixer-retort 3, so as to achieve a high yield of oils.

The solid residue remaining after the distillation of the startingmaterial is preferably used as the heat carrier. Depending on thestarting material, the size of the grains of this residue remainsapproximately equal to the particle size of the starting material, or itmay shrink or swell slightly. In many cases, it may tend to crumble.

The residue that serves as the heat carrier preferably has a particlesize greater than 0.2 mm., so that the separation in separator 2 can beeffected readily with only small quantities of inder dust being carriedinto the condensation apparatus by the vapors and gases. Therecirculation of the heat carriers produces a constant attritioncreating dust, most of which is carried out of the circulating systemwith the combustion gases.

A rather large amount of particulate solid residue is freshly formedcontinuously by the distillation process, and this is removed from thecirculation system as by conduit 61 connected to intermediate hopper 4.At this point, however, there is a portion of freshly distilled residuewhich has not yet passed through the conveying and heating unit 1 andhas therefore a carbon content. To enable the solids residue to be freeof carbon when brought into contace with the air, excess residue can beremoved by line 28 from hopper of the separator through a cooler 43 tothe dump.

The vapors and gases liberated in the distillation are collected at thedischarge end of the mixer-retort 3 in the enlarged gas dome 50, towhich the vapors and gases formed in the intermediate hopper 4 are alsopassed, and from there they are fed through conduit 51 to a dry dust gasseparator 29. The gas separator 29 is preferably in the form of one ormore cyclone separators in parallel or series. The dust that is removedis fed through line 30 into the bottom portion of the intermediatehopper 4 or into line 7, and thence to the conveyor-burner.

The vapors and gases flow from dust gas separator 29 through conduit 68into a cooling or product recovery system 69, in which they are scrubbedand cooled by means of cooled condensate. This treatment is bestperformed in a plurality of stages, three for example. In the firststage 30, the heavy oil condensed is used for the cooling of the vaporsand gases. The heavy oil practically completely absorbs from the vaporsand gases any dust that has not been eliminated by the dry dustseparator. The recirculated oil can be cooled in a heat exchanger 31 bywater, air or the like, or the cooling can also be brought about by theproduction of low-pressure steam. If the utilization of the waste heatis not considered important, one simple solution is to spray water intothe scrubber 30 and evaporate it. The amount of water is then soproportioned and the temperature of the vapors and gases so adjustedthat as much heavy oil condenses in the scrubber as is necessary to keepthe heavy oil with its dust content satisfactorily fluid and pumpable.The vapors and gases are in this case cooled to a temperature between200 and 300 C. The temperature can, however, be reduced still further inorder to make more oil condense and to obtain a more greatly dilutedheavy oil.

In the second stage of the cooling system, in the scrubber 33, the gasesand vapors are cooled by recirculated medium oil to such an extent thatthe oil vapors condense substantially, but no water vapor precipitates.This is the case when the temperature of the vapors and gases at thedischarge of scrubber 33 is slightly above C. The circulating medium oilis recooled for this purpose in a heat exchanger 34 by water, air or thelike. The injection and evaporation of water is impractical in scrubber33, because it is difficult to completely vaporize the water at the lowtemperatures and thus keep the circulating oil free of water. The excessmedium oil taken from the circulation is practically free of dust andwater and can be used directly for further processing or can bedelivered to the storage tank.

In an additional stage of the cooling system 69, the scrubber-cooler 35,the remaining mixture of gases and vapors is chilled to about 30 C. bysprinkling with their own condensate and water. This recirculated wateris best cooled by air in a first cooler 59 and indirectly in a secondcooler 62. The condensed light oils and the gasoline are separated fromthe process water in a separating tank 36. In this cooling stage thelight oils, gasoline and water vapor condense. At this point an indirectcooler with cooling surfaces can also be used. The distillation gaswhich is saturated with water vapor and gasoline vapors at the coolingtemperature, is left behind. The gasoline vapors still contained thereincan be recovered by scrubbing with light oil, by compression of thegases and then cooling them, or also by intense cooling. A portion ofthe light distillation gas is fed back as scaventing gas to themechanical mixer 3 and the intermediate hopper 4.

The light distillation gases have a high content of C to C hydrocarbons,and furthermore contain hydrogen, carbon monoxide and often carbondioxide, too. They have a high heat value and are practically free ofnitrogen. They can be sold as a public utility gas or can be processedto yield synthesis gas or hydrogen.

The combustion gases which have heated and driven the circulating heatcarrier upward in the conveyor-burner unit 1 and have been separatedfrom the carriers in the separator 2 pass from the chamber 14 throughconduit 60 into a cyclone 37 in which the entrained dust issubstantially separated from the gases. This dust can be fed backthrough line 38 into the feed line 5 or directly to the mechanicalmixer-retort 3. Preferably, this dust is ejected from the process, e.g.,through conduit 39, in order to keep the percentage of dust in thecirculating solids low.

It is desirable to connect to cyclone 37 an air preheater 40 and a wasteheat boiler 41 with a steam collector 64 for the production of steam, soas to utilize the waste heat from the waste gases. In some cases itmight be better to place the waste heat boiler 41 first and the airpreheater 40 second in the waste gas line.

In air preheater 40 air is compressed in blower 63, that is needed forthe conveyor-burner 1 and is preheated. It is advantageous to design theair preheater 40 and the waste heat boiler 41 in such a manner that theheat of the waste gases is substantially utilized, but the temperatureshould not be lowered below the dewpoint if the gases contain sulfordioxide.

After the heat of the waste gases has been utilized, dust must bethoroughly removed from them before they can be passed through aSmokestack into the open air. A mechanical or electrical dust remover 42or a conbination of both can be used. This dust remover can also beconnected to a wet scrubber if the circumstances require it. Since theapparatus according to the invention is used in large units of highoutput and consequently very large amounts of waste gases have to bereleased into the atmosphere, their content of fine dust must be verylow. This can only be achieved in may cases by an electrical finecleaning in the final stage. Wet scrubbing is involved when the wastegases are rich in S0 and the S0; is to be recovered.

The dust drawn from cyclone 37 through conduit 39 and from the dustremovers 42 through pipe 67 has to be cooled and moistened so that itcan be handled, transported and dumped without creating a nuisance byproducing great clouds of dust. All of the solid residue that is to bedumped can be introduced into cooler 43. The cooling and moistening ofthe hot residue is performed preferably in a mixer 43 which, like mixer3, contains two mixer shafts rotating in the same direction and equippedwith spirally curved vanes. At the point where the dust is fed in, aline 44 is connected which carries water, preferably condensate producedin the process. By the spraying in and evaporation of the water the dustis cooled to a temperature below 100 C. and can be brought to a moisturecontent either of 24 4 percent, for example, or as high as to percent,if desired.

If the apparatus according to the invention is used for the distillationof coals, large quantities of coke are produced in addition to tar. Thiscoke is used as the circulating heat carrier and is consumed in smallquantity to supply the fuel requirement in the conveying and heatingunit 1. The large mass of the coke ejected from the circuit can beburned in a power plant or, if it is possible and profitable, it can beused as a sintering fuel, as a leaning material in coking works, or as atarfree reducing fuel in dust form. This residue coke can also bebriquetted and the briquettes can be treated to serve for house heatingpurposes or as blast-furnace coke. In the distillation of coal,experience dictates the maintenance of a temperature between 550 and 650C. at the discharge of the mixer-retort 3 and in the intermediate hopper4 in order to obtain a maximum yield of tar. Experience shows that thisyield amounts to about 100 to 170 percent, depending on the type ofcoal, of the tar content that can be detected in the starting coal bythe low-temperature carbonization analysis according to Fischer andSchrader. The apparatus is suitable for use both with coking and withnon-coking coals.

Oil shale has an oil content of 2 to better than percent by weight,depending on its source. Oil shales of different types and origins canbe processed in the apparatus according to the invention. Experienceshows, however, that the oil content should not be less than 8 percent,and preferably not less than 10 percent, in order to make itsufficiently profitable to work. In detail, profitability depends on thecose of decomposing the oil shale, the region in which the oil shale islocated, and the price of natural petroleum at the point of use of theshale oil. A special economic advantage is had when the oil-shaleresidue can be used in whole or in part for special purposes and doesnot have to be simply wasted by dumping it. Depending on the compositionof the residue, it can be used as a hydraulic binder, as raw materialfor the manufacture of cement, for the production of bricks, or for therecovery of aluminum oxide, uranium oxide or the like.

Oil shale having an oil content of more than 20 percent is often plasticby nature, or becomes plastic upon passing through a certain temperaturerange. The apparatus according to the invention can be operated withoutany trouble even with oil shales that behave plastically in the cold orhot state.

The oil yield from oil shale differs according to its character. Incomparison with the oil production that can be achieved in the Fischeranalysis, yields between 95 and 110 percent by weight are achieved inthe apparatus according to the invention.

Oil sands are often hard to work, because they may become plastic evenat temperatures of around 20 C. and tend to cake up. By the use ofappropriate mechanical crushers, especially toothed roller mills, acrushing to under 10 mm. can be achieved. If the broken material has anundesirable tendency to cake up before its introduction into themechanical mixerretort 3, it is advantageous to add finely granularresidue from the distillation of the oil sand to the crushed materialimmediately after it is crushed, thus keeping it from sticking together.Often the oil sand has a tendency to stick undesirably to the walls ofthe crushers and transporting means. This sticking can be completelyprevented if the walls are heated by low-pressure steam or the like.

In oil sand, the oil is present in petroleum form. The same is the casewith oil shale. In the case of distillation in the apparatus accordingto the invention, an oil yield of percent of the oil contentdeterminable by extraction can be achieved if the proper distillationtemperature is maintained and the residence time of the oil vapors inthe hot part of the apparatus is kept short. By using a somewhat higherdistillation temperature, the character of the overall oil productioncan be improved, with a lower overall yield.

The apparatus according to the invention can be made in large units ofhigh output capable of distilling 200 to 400 metric tons per hour ofcoal, oil shale, oil sand or the like. If a total oil yield of 10percent by weight is assumed, 20 to 40 metric tons of oils can beproduced per hour in one unit, corresponding to 160,000 to 320,000 tonsof oil per year. The. inside diameter of the conveying and heating unit1 should not be much greater than 1,500 mm., on the basis of pastexperience. For high throughputs, therefore, 2 to 4 conveying units canbe connected in parallel to one sifter 2. FIG. 4 indicates how, in anapparatus having a plurality of parallel conveying units, the separatingchamber 13 of the sifter 2 is subdivided by cross partitions 44, so thatif one conveying unit fails it will not be packed full by the othersthat are in operation.

The capacity of the mechanical mixer-retort 3 is also limited. In thecase of a temperature difference of C. between the hot heat carrierflowing into the distillation chamber 3 and the solids emerging from theintermediate hopper 4, the amount of circulating solids that is requiredis normally 4 to 8 times the weight of the starting material that has tobe distilled. Consequently the distillation of 200 to 400 tons ofstarting material per hour requires 800 to 3,200 tons of circulatingsolids per hour. The mixing together of these great quantities isadvantageously divided among a plurality, preferably two to fourmixer-retorts 3, which are disposed and operated in parallel underneatha common separator 2. Whether to associate a separate intermediatehopper with each mixer-retort 3 must be decided from case to case. FIG.4 is a top view of a cross section through the apparatus 2 with theopenings of three parallel conveying and heating units 1 in theseparating chamber 13 equipped with the partition and the twocross-partitions 44. Two mixers 3 and one intermediate hopper 4underneath the apparatus 2 are indicated by broken lines.

What is claimed is:

1. In an apparatus for the dry distillation of finely divided solidhydrocarbonaceous material by admixing therewith in a distillationretort a hot finely divided heat carrier taken from the soliddistillation residue of said dry distillation, which heat carrier isthereafter separated from the vaporous distillation product and conveyedpneumatically, separated from the conveying gas and after reheating isrecycled to said distillation retort, said apparatus comprising a. saiddistillation retort having an elongated casing with a feed end portionand a discharge end portion, and a pair of rotating worms in saidelongated casing,

a feed conduit for said hydrocarbonaceous material and c. a separatorcontaining said hot heat carrier connected to the feed end of saiddistillation retort,

. a product recovery and cooling system adapted to receive vaporousdistillation product,

e. an intermediate hopper adapted to receive solid distillation residueconnected to the discharge end of said distillation retort, and

f. a vertical pneumatic conveyor connecting said intermediate hopper andsaid separator, the improvement comprising I. inlet conduit means forintroducing a free oxygen containing propellant gas upwardly through thelower end of said vertical pneumatic conveyor to burn at least a part ofthe carbonaceous material in said carrier material to heat it bycombustion, and a concentric annular chamber about said inlet conduitmeans adapted to receive said carrier material to be heated from saidintermediate hopper, said inlet conduit means having openingscommunicating with said annular chamber,

and controlled gas introduction means communicating with said openingsso as to regulate the amount of said heat carrier material passingtherethrough,

II. a first separator to receive the hot carrier material Ill. a secondseparator to receive gaseous combustion products from said firstseparator to separate entrained dust therefrom,

IV. indirect heat exchange means connected to said second separator, totransfer heat from said hot gaseous combustion products to said freeoxygen containing propellant gas for introduction to said lower end ofthe vertical pneumatic conveyor, and

V. conduit means adapted to remove solid distillation residues from saidtwo separators and said intermediate hopper connected to a mixing devicefor cooling and quenching with water said solid distillation residuesfor disposal.

2. The apparatus of claim 1 wherein said first separator has across-sectional area in the range of 5 to 20 times the averagecross-section of said vertical pneumatic conveyor and the distance fromthe discharge end of said conveyor to the top of said first separator inthe range of 3 to 10 m.

3. The apparatus of claim 1 wherein at least two of said conveyorsoperate in parallel and commonly discharge into said first separator.

4. The apparatus of claim 1 including valve means in said solidsdischarge conduit from said first separator and in said conduit betweensaid intermediate hopper and said annular chamber, said valve meanspermitting the build-up of solids in the conduits and said intermediatehopper.

5. The apparatus of claim 1 wherein said product recovery and coolingsystem comprises three scrubbers adapted to progressively cool saiddistillation vapors by contact in each with cooled liquid condensate.

6. The apparatus of claim 1, wherein said mixing device for waterquenching the discharged solids is connected to said product recoveryand cooling system so as to receive condensed water therefrom.

7. The apparatus of claim 1, including a dust gas separator connected tosaid distillation chamber and to the intermediate hopper so as toreceive distillation vapors from said distillation chamber and todischarge dust recovered therefrom to the intermediate hopper.

2. The apparatus of claim 1 wherein said first separator has across-sectional area in the range of 5 to 20 times the averagecross-section of said vertical pneumatic conveyor and the distance fromthe discharge end of said conveyor to the top of said first separator inthe range of 3 to 10 m.
 3. The apparatus of claim 1 wherein at least twoof said conveyors operate in parallel and commonly discharge into saidfirst separator.
 4. The apparatus of claim 1 including valve means insaid solids discharge conduit from said first separator and in saidconduit between said intermediate hopper and said annular chamber, saidvalve means permitting the build-up of solids in the conduits and saidintermediate hopper.
 5. The apparatus of claim 1 wherein said productrecovery and cooling system comprises three scrubbers adapted toprogressively cool said distillation vapors by contact in each withcooled liquid condensate.
 6. The apparatus of claim 1, wherein saidmixing device for water quenching the discharged solids is connected tosaid product recovery and cooling system so as to receive condensedwater therefrom.
 7. The apparatus of claim 1, including a dust gasseparator connected to said distillation chamber and to the intermediatehopper so as to receive distillation vapors from said distillationchamber and to discharge dust recovered therefrom to the intermediatehopper.